United Launch Alliance’s Delta IV Heavy readies for final flight

United Launch Alliance’s Delta IV Heavy is currently scheduled to make its final flight on Thursday, March 28th, from Space Launch Complex 37B at Cape Canaveral Space Force Station in Florida.

This final flight will conclude just over three decades of missions for the Delta IV family of launch vehicles, which primarily sent classified payloads for the United States government into various orbits from its launch pads in Florida and California.

Like most of its previous missions, this mission will send a classified payload to orbit for the National Reconnaissance Office.

The Delta IV Heavy consists of three Delta rockets strapped together, each powered by a single Aerojet Rocketdyne RS-68A engine, which uses liquid hydrogen and liquid oxygen. The heavy variant of the rocket flew 16 times, including the first Orion capsule test flight. The Delta IV family has launched three variants: the Delta IV Medium, Delta IV Medium+, and Delta IV Heavy.

The Delta IV consisted of just a single common core booster that flew just three times. The Delta IV Medium+ added to its thrust capabilities by strapping on anywhere between two and four solid rocket boosters. The Medium+ variant took its final flight in August 2019, launching a GPS satellite for the U.S. Air Force after a total of 29 launches.

Delta IV Medium on its final flight (Credit Richard Angle)

The rocket was designed to be part of the U.S. Air Force’s Evolved Expendable Launch Vehicle program and didn’t see any real competition for contracts until SpaceX qualified the Falcon 9 and Falcon Heavy, which was able to compete for contracts at a much lower cost. This ultimately led to the retirement of the Delta IV and the introduction of the Vulcan rocket, which is much cheaper and can fly in many configurations to fit mission requirements.

This final launch of the Delta IV Heavy will mark the end of an era for United Launch Alliance as it transitions to the much more versatile Vulcan rocket and rumors of its eventual sale, potentially to Jeff Bezos’s Blue Origin launch company, which is gearing up for the maiden launch of its own giant rocket, New Glenn.

Questions or comments? Shoot me an email at rangle@teslarati.com, or Tweet me @RDAnglePhoto.

Richard Angle: Launch journalist, specializing in launch photography. Based on the Space Coast, a short drive from Cape Canaveral and the SpaceX launch pads.
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